This invention relates to an occlusion device for the closure of physical anomalies like vascular or septal apertures, such as patent ductus arteriosus, patent foramen ovale, atrial septal defects, or ventricular septal defects. The invention comprises a center section extending in an axial direction, upper and lower stranded wire elastic shape memory fixation devices emanating from the center section, with first and second sheets of polyvinyl alcohol foam attached to the fixation devices. The stranded wire elastic shape memory fixation devices are formed from multiple wire strands. This formation greatly increases the resistance to fatigue of the fixation devices and significantly extends the life of the devices after implantation in a patient.
Normally, permanently repairing certain cardiac defects in adults and children requires open heart surgery. Open heart surgery is risky and painful. To avoid it, modern occlusion devices have been developed are that small, implantable devices capable of being delivered through a catheter. Rather than surgery, an occlusion device is deployed by a catheter inserted into a major blood vessel, a procedure that is performed in a cardiac cathlab and avoids the risks and pain associated with open heart surgery. These modem occlusion devices can repair patent ductus arteriosis, patent foramen ovale, atrial septal defects, ventricular septal defects, and other cardiac and non-cardiac apertures.
One such device, disclosed in PCT application PCT/US98/15961, entitled Occlusion Device for the Closure of a Physical Anomaly Such as a Vascular Aperture or an Aperture in a Septum, filed on Jul. 31, 1998 by Bernhard Schneidt, discloses a non-thrombogenic occlusion device that is insertable into an anomaly via a catheter. In addition, a similar device filed as German Appln. 297 14 242.9 on Aug. 8, 1997, discloses an occlusion device which can be inserted via a catheter.
The new occlusion devices that are inserted via a catheter include button devices, collapsible umbrella-like structures, and plug-like devices. One major draw back is that the intent of some of these occlusion devices is to fill the ductus and stimulate thrombosus, or a blood clot. Once the blood has clotted around the device, tissue begins to grow thus ensuring that the ductus is permanently closed. Blood clots, however, are potentially dangerous in that they may dislodge, get carried to the brain and cause a stroke.
Occlusion devices with umbrella-like structures use a system of small metal wires to hold the occlusion device in place. Due to the severe environment the human heart presents, including a continuous cycling of up to 5 billion pulses over the lifetime of a human, the wires may develop fatigue failure problems. With each pulse, the wires are strained and eventually may fracture or break, giving rise to potential complications and patient anxiety. In addition to the stress caused by the beating of the heart, metal wires may also be strained when a device is inserted into an irregularly shaped opening. For instance, one side of the opening may only be a few millimeters thick, but another side may be many more millimeters thick. Thus, one side of the occluding device may be bent open ether than the other side, putting more stress on the wires used on that side. This stress from being deformed and bent may also lead to fatigue failures.
Efforts to alleviate the fatigue failures described above include varying the shape and diameter of the wires used in occlusion devices. However, increasing the diameter of the wire can actually result in the wires becoming more brittle and more susceptible to fatigue failure and fracturing. Another effort to prevent failure of the wire is to use coils or hinges. The coils and hinges attempt to distribute the forces acting upon the wires, and prevent the problems with fatigue failures. However, the coils and hinges do not significantly decrease fractures or failures in the wires. So far, nothing has dealt satisfactorily with the fatigue failures in the wires.
Thus, there is a need in the art for an occlusion device that is collapsible enough to fold into a small catheter and constructed of materials that will not cause blood clots. In addition, there is a need for an occlusion device that is durable enough to withstand the heart's pulsing without experiencing fatigue failure.